Electrophoretic deposition (EPD) is one of the electrochemical processes attracting increasing interest as an efficient material processing technique for producing films and coatings from colloidal suspensions. EPD is commonly used in processing of ceramics, coatings and composite materials. Interest in the EPD technique is driven not only by its applicability to a wide range of materials but also by its simplicity and cost-effectiveness. It essentially requires simple equipment, as well as being amenable to scaling-up.
Electrophoretic deposition is achieved via the motion of charged particles, dispersed in a suitable solvent, towards an electrode of opposite charge under an applied electric field. This process results in the accumulation of particles and the formation of a homogeneous and rigid deposit at the deposition electrode. Beyond its application for production of functional and composite ceramics, layered and functionally graded materials, composite coatings and biomaterials, EPD has also been used for deposition of nanoparticles such as carbon nanotubes to produce advanced nanostructured materials. It has been reported that large scale, homogeneous multi-walled carbon nanotube (MWCNT) films with good electrical and field emission properties were obtained using EPD for 2 minutes under DC voltage of 200-300V.
Pulse electrophoretic deposition method is one of several EPD techniques. In this method, an electric current in the form of series of pulses is passed between two electrodes instead of a constant DC current. U.S. Pat. No. 4,496,436 discloses an improved pulse method for electrodeposition and an apparatus for carrying out this method. In another report, the application of pulse potential of suitable width to an aqueous suspension of alumina enables obtaining smooth and bubble-free deposit; however, the application of continuous DC resulted in incorporation of bubbles in the deposit. Furthermore, U.S. Pat. No. 4,789,437 discloses a pulse electroplating process for producing crack-free rhodium electrodeposits on different metal substrates and to form electrochemically thin rhodium sheets or foils. U.S. Patent application No. 2005/0205425 A1 discloses a process involving pulse electrodeposition for forming coatings of nano-crystalline metals, metal alloys or metal matrix composites where the process can be applied to establish wear-resistant coatings and foils of pure metals or alloys of metals.
There is a need for low cost stable chiral nematic films of cellulose nanocrystals, preferably produced by a simplified ecofriendly process.